Distribution of the 26 major OTUs.

The 26 OTUs accounted for more than 1% in each sample, and the minor groups denote the sum of rare OTUs that were arbitrarily defined as having a frequency of <1% within a sample. Numbers in parentheses indicate the salinity of each sample. Abbreviations in parentheses: GP, Gammaproteobacteria; AP, Alphaproteobacteria; FB, Flavobacteria; GPB, Gram-positive bacteria.